Method of forming polygonal bores.



J. W. MEAKER.

METHOD OF FORMING POLYGONAL BORES.

APPLICATION FILED JULY 7; 1913- 1,144,425a Patented June 29, 1915.

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JOHN W. MEAKER, 0F DETROIT, MICHIGAN.

METHOD OF FORMING POLYGONAL BORES.

atters.

To all whom it may concern Be it known that 1, JOHN W. MEAKER, a citizenof the United States of America, residing at Detroit, in the county ofWayne and State of Michigan, have invented certain new and usefulImprovements in Methods of Forming Polygonal Bores, of which thefollowing is a specification, reference being had therein to theaccompanying drawings.

It is frequently desirable to form a ferrule, bushing, collar, check-nutor like fittings with internal squared or polygonal bores or boreshaving facets whereby a plug, wrench or tool may be inserted for turningthe part in or out of engagement with some engaging member. This isdifiicult as it requires both time and power to cut away the metal fromthe interior and if the article have a light thin wall, it is almostimpossible to prevent deformation of the exterior.

This invention relates to a method of forming a square or polygonal borein a bushing or the like and more especially in such an article having acomparatively thin wall which is easily and cheaply carried out in suchmanner that the exterior is not changed thereby.

The invention also includes the bushing or like article formed by suchprocess.

In the drawings, Figure 1 is a view of a blank bored and tapped forbroaching; Fig. 2 is a view thereof in longitudinal section; Fig. 3 isan end view of a finished bushing; Fig. 4c is a view in longitudinalsection thereof; Fig. 5 is a view of one form of the broach; and Figs. 6and 7 are views in detail of another form of broaching tool.

As an initial step in the process a blank 1 is formed of the desiredexterior conformation, as for example. with exteriorscrewthreadedperiphery. The blank is drilled out to a diameter slightly less thanthat of the desired finished polygonal bore. Screw threads 2 are thencut in the blank as a second step in the process by forcing a suitablethreading tap therethrough in the usual manner. A broach of the squareor poly onal form desired. whose greater diameter is slightly longerthan the greatest diameter of the screw threads, is then forcedlongitudinally through the threaded blank, as the Specification ofLetters Patent.

Application filed. July 7, 1913.

Patented June 29, 1915..

Serial No. 777,742.

final step of the method. Because of the proportions of the broach anddie, the corners of the broach enter and plane out the corners of thebore sharply and clearly from the wall of the blank while theintermediate portions of the cutting edges of the tool sever or planeoff the projecting portions of the screw thread toan extent dependent onthe distance from the corners. The carrying away or weakening of thesurface by the initial use of the tap permits the broach 'to readilyplane oif the bulk of the remainder of the metal and to clear the chipsfrom its path without difliculty. As a convenient arrangement forcarrying out the method, the blank may be turned up and drilled in alathe or screw machine, and a broach as in dicated at d carried in thesame machine, with a properly proportioned pilot tap 5 then be turnedinto the blank or the blank rotated on to the tap until the latter haspassed through. Then by manual operation of the carriage on which eitherthe broach or the blank is mounted, or by power, the broach is readilypushed through. Or the blank may be screwthreaded by any suitablydimensioned tap and the broach 6 shown in Figs. 6 and 7 be used. a pilotmember 7 centering the broach in the bore. The effort required isslight, and the broach has no expanding or disrupting effect sufiicientto distort even a comparatively thinwalled bushing. sleeve, collar, nutor whatever fitting is thus treated. A bore is formed which is of thedesired contour and dimensions and which makes a good seat for theapplication of a plug wrench or tool.

Obviously, changes in the details of construction may be made withoutdeparting from the spirit of the invention and I do not care to limitmyself to any particular form or arrangement of parts.

What I claim is 1. A. method of forming a bore having facets in a metalarticle which consists in drilling the article. cutting an interiorscrew thread in the resultant opening and forcing a broach of thecontour of the desired bore through the screw threaded aperture.

2. A method of forming a bore having facets in an article which consistsin removing a portion of the metal around the bore by cutting a screwthread therein, and then forcing a broach longitudinally through the inpresence of two Witnesses. article Whose greatest diameter is slightlyJOHN W. MEAKER.

longer than the greatest diameter of the VVitnesse's: 5 screw thread,and Whose cross-sectional con- C. R. STIOKNEY,

tour is that of the desired faceted bore. A. M. Donn.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of ratents,

Washington, D. 0."

In testimony whereof I afiix my signature

